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Including small trees and shrubs
in your plan will enhance the site
as they grow into maturity.
Planting in containers which can
then be placed under trees or in
other shady locations is another
way to grow plants which cannot
tolerate full sun.
Dirt is another factor. Yours will
be some combination of soil, silt,
sand, and clay, but the
proportions are very important
when deciding which species of
plants are likely to thrive.
We tend to think of forests as
having rich, loamy soil, but there
are also woodlands which are very
dry, or so wet that they are
waterlogged much of the time.
To determine the soil
composition in your site, dig down
about 8" and put two cups of dirt
in a jar. Fill it with water, put a top
on it, shake it hard, and then let it
sit for 24 hours. The organic
material will now be floating on the
top, and underneath it will be
layers (in this order) of clay, silt,
and sand.
Usually the ideal woodland soil
has a high percentage of organic
matter and silt. Raking up the
leaves under the trees each fall,
as current gardening practices
tend to dictate, interferes with
the natural recycling process.
If you are concerned about the
leaves matting down over the
winter, shred them and then
return them to the garden bed.
This is a much safer way to
improve the soil under trees than
to till in compost or other
amendments. Disturbing the soil
or dramatically changing its
depth will often harm the roots of
mature trees.
Returning to the hole that you
dug, fill it with water and wait six
hours. If the water is still there,
you will want to choose plants
that thrive in wet conditions.
As a rule, the soil under groups
of conifers will be dry and lacking
in organic matter, because the
needles block rainwater from
reaching the ground. Similarly,
older trees on suburban lots tend
to have dry, infertile soil at their
base because of their shallow,
spreading roots.
Rather than trying to
drastically change the soil and
moisture conditions, which could
damage the mature trees that
you want to retain, choose plants
in smaller containers so they can
be fitted into the spaces between
shallow roots, add small
deciduous trees which will shed
their leaves and gradually add
organic matter to the soil, and
mulch with compost.
It’s a good idea to test the pH
of your soil. If your site is under
conifers and deciduous trees, it
will tend to be more acidic.
Property near construction sites
or limestone rock formations is
likely to be alkaline.
Most of the woodland plants
that you buy at a nursery prefer a
more acidic soil, with a pH of 6-
6.5. Azaleas and rhododendrons,
two of the most popular shrubs
for shady areas, like a pH closer to
5.5. There are many inexpensive
kits available to test the pH of
your soil, and it’s a good idea to
check it in several spots if your
garden area is large.
Although tall trees block a
certain amount of rainfall, the
water that does reach the plants
beneath them tends to stay on
the foliage longer than in a sunny
environment, and this can promote
disease.
Some careful, modest pruning of
lower limbs or thinning of the
branches (not more than 1/3 per
year) can increase air circulation,
and you shouldn’t place the plants
as close together as in a sunny
location.
It’s a good idea to water plants
with soaker hoses or drip
irrigation rather than wetting the
leaves, and it’s better to water
deeply and then allow the soil to
dry out somewhat before watering
again. This will encourage deeper
roots as well as discourage
disease.
In nature, many plants manage
to co-exist in limited space
because some have deep roots,
others are shallow, and still others
use surface rhizomes. By copying
that pattern, you can increase the
diversity in your own garden.
Plants in natural settings also
exhibit a variety of growth
patterns. Some appear early in
the year, before leaves on the
trees block the sunlight, and then
go dormant.
Others are evergreen, allowing
them to produce food year-round,
taking advantage of whatever light
is available.
In addition, in nature you will find
that plants grow in “layers." There
are tall trees, then a shorter
understory of smaller trees and
“Trees provide a sheltering umbrella during hot
summer days, and mute harsh summer light to a
verdant, luminous quality. They create an incomparable
sense of place and enclosure as well as valuable
habitat for wildlife."
– Brenda Skarphol in Woodland Gardens, Brooklyn Botanic Garden Series
